A conventionally known machine tool includes: workpiece holding means configured to hold a workpiece; a cutting tool rest configured to hold a cutting tool for cutting the workpiece; feeding means configured to feed the cutting tool toward the workpiece in a predetermined feeding direction by allowing relative movement between the workpiece holding means and the cutting tool rest; repetitive movement means configured to repetitively move the workpiece holding means and the cutting tool rest relative to each other by repeating the relative movement in the feeding direction at first and second speeds different from each other; and rotating means configured to rotate the workpiece and the cutting tool relative to each other. An example of such a machine tool is described in United States Patent Publication No. 2014/0102268, published on Apr. 17, 2014.
A control apparatus of the machine tool is configured to control the rotating means, the feeding means, and the repetitive movement means to drive, and to allow the machine tool to machine the workpiece by the relative rotation between the workpiece and the cutting tool and by the feed movement of the cutting tool toward the workpiece with the repetitive movement in the feeding direction.
The conventional machine tool is configured so that an operation instruction is issued by the control apparatus at a predetermined cycle. Therefore, a repetitive movement frequency at which the workpiece holding means and the cutting tool rest are repetitively moved relative to each other is defined as a limited value attributable to a cycle during which an operation instruction can be issued by the control apparatus. However, the repetitive movement frequency is not considered in the conventional machine tool. Therefore, with respect to any number of rotations of the relative rotation, the repetitive movement may not be performed at any number of repetitions of the repetitive movement of the cutting tool relative to the workpiece during one rotation of the workpiece.
Thus, the present invention is intended to solve the above problem of the prior art. That is, it is an object of the present invention to provide a control apparatus of a machine tool that feeds a cutting tool in a feeding direction while repetitively moving the cutting tool, and that can smoothly cut a workpiece while easily separating chips. It is also an object of the invention to provide a machine tool including the control apparatus.